The reaction `A(g)toB(g)+2C(g)` is a first order reaction with rate constant `2.772xx10^(-3)s^(-1)`, Starting with `0.1` mole of A in 2 litre vessel, find the concentration of A after 250 sec when the reaction is allowed to take place at constant pressure and at 300 K?
A. `0.0125 M`
B. `0.025 M`
C. `0.05 M`
D. none of these